The present invention relates to a control installation for use with an internal combustion engine operating with exhaust gas recycling which has an exhaust gas recycling valve disposed in a return line branching off from an exhaust pipe of the engine and terminating in a suction tube thereof downstream of an arbitrarily settable throttle flap valve of the engine which is mounted within the suction tube with the position of the recycling being controlled in dependence on the pressure in the suction tube.
In order to reduce the components in the exhaust gas of an internal combustion engine which are detrimental to health, especially for reducing the components of NOx, a very effective means is the recycling of certain quantities of the exhaust gas. This addition of a gas which does not take part in the combustion process results in a reduction of the combustion temperature, so that less nitric oxide is formed. On the other hand, however, this inert gas reduces the cylinder charge during full-load operation and it deteriorates the smooth running of the engine at low rpm, the effect of which is especially pronounced during idling operation. In order to maintain maximum performance during full-load operation, and in order to guarantee quiet running of the engine during idling operation, exhaust gas recycling should not take place in these domains.
During idling operation, the exhaust gas emission is low because the throughput of gas and the cylinder charge are both small. In addition, the combustion temperatures are lower, and therefore also the emission of nitrogen. In the partial-load domain, however, the nitrogen emission is particularly high and therefore especially dangerous. It is dangerous because in city operation, where the most stringent regulations prevail with respect to exhaust gas emissions, most driving is done in the partial-load domain. Where it is desired, however, during a short term full-load operation, such as may occur for example during the passing of another vehicle, the exhaust gas recycling is not interrupted. In cross-country operation the regulations are less stringent and the maximum performance is required under full load and the accumulation of toxic exhaust gases is lower.
Only during in-town driving which is subject to particularly stringent regulations (CVS-Test) and where the emission is especially great, the exhaust gas is re-cycled under the ware and short-time full load conditions prevailing there.
This load dependent control occurs with the aid of an exhaust gas recycling valve. This recycling valve must firstly be sealed with respect to the atmosphere in order to prevent the intrusion of leakage air into the suction tube of the engine which could result in rendering the fuel-air mixture unstable. Secondly, it requires high temperatures at its valve seat in order to avoid a deposition of exhaust gas components there. The sealing with respect to the atmosphere is achieved by elastic means which are relatively heat sensitive. It would therefore be desirable to provide means for cooling the area of the recycling valve between the valve seat and the sealing element.